反激变换器共模传导EMI噪声抑制的研究

Research on CM EMI Suppression in Flyback Converter

对反激式变换器的原、副边共模传导EMI噪声特点进行了分析,总结了共模传导噪声模型并详细介绍了干扰源、传输通道对共模传导噪声的影响。建模分析了变压器绕组分布电容与共模传导等效电容之间的关系,针对原、副边共模噪声的特点,提出通过调整变压器绕组层间距离来控制共模传导路径阻抗特性的新方法,实现原、副边共模电流的抵消,从而更好地抑制共模传导噪声。并以一台40W的反激式电源为实验平台,用实验方法验证了该方案的可行性。

Common-mode （CM） conducted noise characteristic of flyback converter was analyzed. A model of CM conducted noise was concluded. The influence of CM noise sources and its conduction paths on CM noise were introduced with circumstance. The relationship between the equivalent CM capacitance of transformer and the stray capacitance was analyzed detaileclly. A new solution adjusting the distance between the primary winding and the second winding to repress the CM conducted noise was proposed. The experiments carried based on a 40W flyback converter verify the validity of the new solution.